At each of the RAPTOR-A and -B observatories, four 85-millimeter telephoto
lenses provide four digital images that are stitched together to form
a 38- by 38-degree wide-field image. On the left is a RAPTOR-A wide-field
image of the Orion constellation. At the upper left, the reference star
marked by a vertical line is Betelgeuse. The reference star at the lower
right (in Orion's foot) is Rigel. To search for a transient optical
event, RAPTOR's computers measure the positions and brightnesses of
up to 250,000 objects in each wide-field image and compare their positions
and brightnesses to those of known celestial objects—all in 10 seconds
or less. If the computers find an object that appears to be a transient
optical event, RAPTOR zooms in with its narrow-field lenses to take
movies of the object. On the right is a 4- by 4-degree narrow-field
image taken by RAPTOR-A's 400-millimeter telephoto lens. The three brightest
reference stars marked by horizontal lines are the main stars in Orion's
belt.